In a modern air conditioning system a heat exchange fluid, typically a form of Freon in a home or small commercial system, circulates in a closed system comprising a compressor, a first heat exchanger [condenser], a flow restriction and second heat exchanger called an evaporator. The heat exchange medium is compressed in the compressor and exits in the vapor phase at high temperature [from heat of compression] and high pressure. This returning gas flows to the outdoor heat exchanger or condenser, a series of coils containing the Freon or other heat exchange medium where air from outside the area to be cooled flows across the hot gaseous fluid containing coils and extracts heat from the fluid causing the fluid to condense to the liquid phase as it progresses through the coil, becoming totally fluid before the end of the coil. The reminder of the coil is used to subtract additional heat from the Freon before it leaves the condenser via the liquid line.
The fluid, now at ambient temperature in liquid phase and still at high pressure, enters the flow restriction. It expands as it exits the flow restriction. As a result of expansion and vaporization, the fluid exits as a mixed liquid/vapor at low temperature and pressure.
The fluid then enters the evaporator, a series of coils where a fan causes the hot air to be cooled to flow over the coils thereby transferring heat from the hot air to the fluid and changing it to the vapor phase as it warms. The low pressure fluid travels to the compressor where the compressor pumps the returning fluid to the condenser, where outside air is drawn across it by a fan as the cycle begins again.
In a central air conditioning system, the air contained in the space to be cooled is moved through a return air duct by a fan located in the air handling unit and then through a evaporator where the air is both cooled and dehumidified. The conditioned air is then distributed through the supply ductwork back to the space and the cycle repeats itself until the desired conditions are obtained. In a room air conditioner the air flowing across the evaporator is discharged directly into the room.
Various types of coolant fluids are in use to cool the air, such as Freon, water, or a water-gylcol mix.
As the hot room air passes over the evaporator coils and is cooled it is no longer able to hold the quantity of moisture present as water vapor. Droplets of liquid water condense on the surface of the evaporator coils. This condensate water, typically at a temperature of about 40.degree. F., falls from the coils by gravity and is collected, typically in a drip pan. The condensate must be disposed of either by channeling it to a remote drain [in a central air conditioning installation] or by letting it drip from the unit in the case of a window or wall or transom mounted unit.
A common occurrence and nuisance in external wall and window AC units is the condensate water dripping from the unit. The condensate water, formed when hot air is blown across the cooling coils of the AC unit, becomes supersaturated and gives up its excess water as it cools, is usually directed to a drain pan. An overflow from the drain pan exits the unit by gravity and drips onto the ground.
Problems exist with the disposal of this condensate from window, wall or transom mounted units. In apartment buildings the wall units are typically arranged directly beneath each other and the water dripping from a higher unit oftentimes drips onto the lower unit causing an annoying sound offensive to the resident of the lower apartment as well as causing rust or degradation of the case of the lower unit. If the unit is transom mounted, which is often the only area the unit can be positioned in storefront installations, the unit will drip on customers entering or exiting the establishment. Draining the liquid away from the unit is not possible because of lack of drain locations.
The oil or gas shortage of 1974 started the process of increasing air conditioner efficiency. Even so, until about 1980 there was no particular concern about the cost of running an air conditioner as prices in general were fairly low. Air conditioners then began to be designed with efficiency considerations in mind, using fewer or lighter materials, in an attempt to obtain more BTU's/unit of electricity. Electric motors and compressors became smaller and lighter and drew less amperage, becoming more efficient due to advances in electrical engineering. An orifice, an advanced metering device, was designed which would allow a lower head pressure or condensing pressure to be used, which in turn lowered the electric draw the compressor used. In conjunction with this, more coil surface is now used in the condenser to lower head pressure and provide more subcooling of the liquid Freon.
Over the years different various more effective heat transfer fluids were developed. Time delay relays were also developed which delay the evaporator fan [inside fan] from turning on until the compressor runs for about 30 to 60 seconds to start the Freon moving through the inside coil, and which extend fan operation on shutdown for approximately 30 to 60 seconds to take advantage of the Freon still evaporating.
In window units, slingers are in use which throw condensate water onto the condenser coil to help transfer heat in conjunction with the outside air blown across the coil by the fan. This technique helps increase efficiency but not enough of the water hits the hot gas line to evaporate sufficient amounts of the condensate water to eliminate condensate disposal problems. The unevaporated water drains down the coil picking up heat and is warm when it reaches the drain pan from which the slinger draws water. Over a short period of time the water in the pan is warmed so that the efficiency of heat transfer decreases substantially. This results in the liquid line temperature approximating that of the environment, even though the slinger does a good job of cooling the condenser coil.
Attempts have been made to increase efficiency by running the liquid line [usually approximately 2 feet of plain copper tube] through the condensate water drain pan but this provides little benefit because the water is warm. Even were the water cool, the plain copper tube doesn't act as an effective heat exchanger. A copper tube run through the drain pan in a central unit doesn't work for the same reason.
Water cooled condensers were developed early on and are in use in commercial applications using cooling towers, but the residential use of water cooled condensers has never been feasible because of cost or esthetic considerations preventing the use of a residential cooling tower.
Among the improvements that have been implemented is the addition to the system of a small heat exchanger which coils the liquid line around the suction line, subcooling the liquid line while also boiling off any droplets of Freon still remaining in the suction line. This however does not increase the efficiency of the unit as energy is just transferred from one line to the other and was used mainly to protect the compressor from unevaporated droplets of Freon, or in some cases to cool the liquid line.
In summary, AC units have been lightened and made smaller, Freon 22 adopted as the Freon of choice in air conditioning systems [residential--and many commercial installations except for very large units], time delay relays are commonly used on evaporator fans, and lower head pressures are now the norm.
It is an object of this invention to further increase the efficiency of current air conditioning units.
It is a further object of this invention to remove the problems associated with the disposal of condensate water from window air conditioning units and other non-central air conditioning units.